The present invention relates to a delay-locked loop device, and more particularly, to a delay-locked loop device and a delay-locked method thereof which compensates a skew between an external clock and data or a skew between an external clock and an internal clock particularly by applying a single delay model portion, a complementary phase multiplexing, and a cascade delay line.
In general, a delay-locked loop is a circuit which delays an internal clock of a synchronous memory using a clock in a semiconductor memory device to coincide with an external clock without an error. In other words, when a clock coming from the outside is used in the inside, a skew is likely to occur between an external clock and an internal clock or to occur between an external clock and data. Accordingly, a delay-locked loop is often used to reduce such a skew.
In recent years, studies have continued in the direction of how to minimize variable delay times in order to reduce or minimize jitter in delay-locked loops. For this purpose a delay-locked loop is presented having a hierarchical delay line structure which includes a coarse delay line and a fine delay unit.
As an example, a delay-locked loop in a related art, as illustrated in FIG. 1, includes a buffer portion 100, a delay line portion 110, a duty error adjustment portion 120, a first delay model portion 130, a first phase detecting portion 140, a second delay model portion 150, and a second phase detecting portion 160.
The buffer portion 100 receives an external clock signal (CLK) to output a clock input signal, which is activated at an edge of the clock.
The delay line portion 110 receives the clock input signal from the buffer portion 100 and delays the clock input signal for a predetermined amount of time by using a first and a second detection signals provided from a first and a second phase detection portions 140 and 160 in order to output a first and a second clock signals (INTCLK1 and INTCLK2, respectively).
The duty error adjustment portion 120 receives the first and second clock signals (INTCLK1 and INTCLK2, respectively) from the delay line portion 110 and moves each edge of the first and the second clock signals (INTCLK1, INTCLK2) between a falling edge of the first clock signal (INTCLK1) and a falling edge of the second clock signal (INTCLK2) to output a mixed clock signal (INT_CLK).
The first delay model portion 130 receives the clock input signal and makes a replica delay to output as a first delay clock signal (ICLK1).
The first phase detecting portion 140 receives the external clock signal (CLK) and compares with the first delay clock signal (ICLK1) outputted from the first delay model portion 130 to generate the first detection signal.
The second delay model portion 150 receives a signal having an opposite phase to the clock input signal and makes a replica delay to output as a second delay clock signal (ICLK2).
The second phase detecting portion 160 receives the external clock signal (CLK) and compares with the second delay clock signal (ICLK2) outputted from the second delay model portion 150 to generate the second detection signal.
A delay-locked loop in the related art controls a delay amount of the delay line portion 110 by using the first and the second detection signals to align the rising edges of the first clock signal (INTCLK1) and the second clock signal (INTCLK2), and subsequently corrects a duty cycle of the first and the second clock signals (INTCLK1, INTCLK2) using the duty error adjustment portion 120.
At this time, both the first and the second delay model portions 130 and 150 perform a similar type of operation before a duty cycle correction operation. However, the second delay model portion 150 is not used after aligning the rising edges of the first clock signal (INTCLK1) and the second clock signal (INTCLK2) and then operating the duty error adjustment portion 120.
As a result, a delay-locked loop in the related art exhibits an efficiency problem in that an unnecessary amount of current is consumed after starting a duty cycle correction operation. This is because there remains an unnecessary but active circuit, that is, the second delay model part 150, that consumes current and occupies an unnecessary area.
Furthermore, when the second delay model portion 150 is switched to an OFF-state then an instantaneous current is consumed. This switching can generate a jitter which results in a problem that an additional locking time is required due to correct and avoid any adverse affects from this jitter.
On the other hand, the delay line part 110 includes a coarse delay line having a plurality of unit delay cells and a fine delay unit having a phase mixer, and the coarse delay line can be divided into a single coarse delay line in which a plurality of unit delay cells are serially connected and a dual coarse delay line in which coarse delay lines are dually connected.
After a coarse locking by the coarse delay line has been achieved, the delay line portion 110 having a single coarse delay line uses a weight factor during a fine tuning operation in the phase mixer.
At this time, when a shift is generated at a boundary of the phase mixer in the coarse delay line, the weight value should be reset again to maintain an output phase of the phase mixer. If a shift timing of the coarse delay line does not accurately coincide with a reset timing of the phase mixer, then in this case, a jitter can be generated at an output portion of the phase mixer. The delay line portion 110 has a dual coarse delay line having a structure in which two coarse delay lines are connected to a fine delay line, in which each coarse delay line operates with a difference from each other by a unit delay cell. In such a dual coarse delay line, an inputted clock is shifted using an odd-numbered unit delay cell in any one of the two coarse delay lines, and is shifted using an even-numbered unit delay cell in the other one of the coarse delay lines. Therefore a weight factor of the phase mixer does not have to be reset in the dual coarse delay line.
Nevertheless, when a dual coarse delay line is used, a boundary switching problem of the single coarse delay line can be resolved. However there is a problem in that a large area is occupied and also the current consumption is large because coarse delay lines are dually used.